Role of germanium in microstructural development of powder metallurgy Ti-20Cr-xGe alloys

Abstract

This paper investigates the microstructural changes after incorporating germanium (Ge) into a Ti-20Cr alloy fabricated by powder metallurgy. A positive correlation between Ge compositions and density of the sintered alloys was revealed, with limited effects on the grain size. The microstructure comprised equiaxed β phase grains and nodules of eutectoid phases (α + TiCr2). Alloying more Ge to Ti-20Cr produced more α phase and broadened the nodules. This coarsening is believed to be the consequence of increasing (α-β) interfacial area, which serves as the nucleation site for TiCr2. The largest proportion of α phase (~14 vol%) was obtained in the Ti-20Cr-3Ge alloy, together with the formation of Ti5Ge3 intermetallic. The microstructural changes after Ge additions increase hardness by up to 13%, which may enhance the wear resistance of the alloys providing a promising alternative for dental implants.